const PENDING = 'pending'  // 等待
const FULFILLED = 'fulfilled' // 成功
const REJECTED = 'rejected' // 失败

class MyPromise {
  constructor (executor) {
    try {
      executor(this.resolve, this.reject)
    } catch (e) {
      this.reject(e);
    }
  }
  // promsie 状态 
  status = PENDING;
  // 成功之后的值
  value = undefined;
  // 失败后的原因
  reason = undefined;
  // 成功回调
  successCallback = [];
  // 失败回调
  failCallback = [];

    resolve = value => {
      // 如果状态不是等待 阻止程序向下执行
        if (this.status !== PENDING) return;
        // 将状态更改为成功
        this.status = FULFILLED;
        // 保存成功之后的值
        this.value = value;
        // 判断成功回调是否存在 如果存在 调用
        while(this.successCallback.length) this.successCallback.shift()()
    }

    rejected = err => {
        // 如果状态不是等待 阻止程序向下执行
        if (this.status !== PENDING) return;
        // 将状态更改为失败
        this.status = REJECTED;
        // 保存失败后的原因
        this.reason = reason;
        // 判断失败回调是否存在 如果存在 调用
        while(this.failCallback.length) this.failCallback.shift()()
    }

    then (successCallback, failCallback) {
        // 参数可选
        successCallback = successCallback ? successCallback : value => value;
        // 参数可选
        failCallback = failCallback ? failCallback: reason => { throw reason };
        let promsie2 = new MyPromise((resolve, reject) => {
          // 判断状态
          if (this.status === FULFILLED) {
            setTimeout(() => {
              try {
                let x = successCallback(this.value);
                // 判断 x 的值是普通值还是promise对象
                // 如果是普通值 直接调用resolve 
                // 如果是promise对象 查看promsie对象返回的结果 
                // 再根据promise对象返回的结果 决定调用resolve 还是调用reject
                resolvePromise(promsie2, x, resolve, reject)
              }catch (e) {
                reject(e);
              }
            }, 0)
          }else if (this.status === REJECTED) {
            setTimeout(() => {
              try {
                let x = failCallback(this.reason);
                // 判断 x 的值是普通值还是promise对象
                // 如果是普通值 直接调用resolve 
                // 如果是promise对象 查看promsie对象返回的结果 
                // 再根据promise对象返回的结果 决定调用resolve 还是调用reject
                resolvePromise(promsie2, x, resolve, reject)
              }catch (e) {
                reject(e);
              }
            }, 0)
          } else {
            // 等待
            // 将成功回调和失败回调存储起来
            this.successCallback.push(() => {
              setTimeout(() => {
                try {
                  let x = successCallback(this.value);
                  // 判断 x 的值是普通值还是promise对象
                  // 如果是普通值 直接调用resolve 
                  // 如果是promise对象 查看promsie对象返回的结果 
                  // 再根据promise对象返回的结果 决定调用resolve 还是调用reject
                  resolvePromise(promsie2, x, resolve, reject)
                }catch (e) {
                  reject(e);
                }
              }, 0)
            });
            this.failCallback.push(() => {
              setTimeout(() => {
                try {
                  let x = failCallback(this.reason);
                  // 判断 x 的值是普通值还是promise对象
                  // 如果是普通值 直接调用resolve 
                  // 如果是promise对象 查看promsie对象返回的结果 
                  // 再根据promise对象返回的结果 决定调用resolve 还是调用reject
                  resolvePromise(promsie2, x, resolve, reject)
                }catch (e) {
                  reject(e);
                }
              }, 0)
            });
          }
        });
        return promsie2;
      }

      finally (callback) {
        return this.then(value => {
          return MyPromise.resolve(callback()).then(() => value);
        }, reason => {
          return MyPromise.resolve(callback()).then(() => { throw reason })
        })
      }

      catch (failCallback) {
        return this.then(undefined, failCallback)
      }
      static all (array) {
        let result = [];
        let index = 0;
        return new MyPromise((resolve, reject) => {
          function addData (key, value) {
            result[key] = value;
            index++;
            if (index === array.length) {
              resolve(result);
            }
          }
          for (let i = 0; i < array.length; i++) {
            let current = array[i];
            if (current instanceof MyPromise) {
              // promise 对象
              current.then(value => addData(i, value), reason => reject(reason))
            }else {
              // 普通值
              addData(i, array[i]);
            }
          }
        })
      }
      static resolve (value) {
        if (value instanceof MyPromise) return value;
        return new MyPromise(resolve => resolve(value));
      }

}

let promise = new MyPromise((resolve, rejected) => {
    resolve('1000')
}).then(res => {
    console.log(res)
},err => {
    console.log(err)
})

function resolvePromise(promise2, x, resolve, reject) {
    if (promise2 === x) {
        return reject(new TypeError('重复引用了'))
    }
    if (x instanceof MyPromise) {
        // x.then(value=>resolve(value),err=>reject(err))
        x.then(resolve, reject)
    } else {
        resolve(x)
    }
}

module.exports = MyPromise;